Raw gas exiting through exhaust? What the hell!

[Machinehead]

HI, any help will be appreciated. I have a 91 explorer 4.0 pushrod v6. Large amounts of gas come through the exhaust and it runs rough. What is going on? It leaks right out of the tailpipe and a puddle of gas will form within seconds. I talked to a mechanic and he said the injector was stuck open so I put all new injectors and it still does it! Could it be the fuel rail cracked? I am stumped, HELP!

[KC Ron Carter]

If you have a miss, the fuel not burnt will end up being consumed in the catalyst if you have one installed.

If no catalyst and a miss this would explain the fuel.

I use a inductance pickup timing light as a shady scope to make sure if the issue is ignition or compression. I am sure it is getting fuel.

If all cylinders are firing normal on the timing light I would open the hood after dark and look for cross fire on the plug wires. If the wires need replaced also consider changing the cap and rotor.

If there are no other issues noted I would then suggest a compression test.

Later,

[454Casull]

It uses a distributor?

[Machinehead]

Hey thanks for the info. Although Ive checked the spark with the timing light and it was ok. I also checked the compression and there was a 17 pound differential between cylinders which isnt great but should still work fine. It has brand new wires and plugs and I pulled the new plugs recently and about half looked like new and the other half were all black already? SO it leads me to believe that only certain cylinders are getting too much gas and not firing, I suppose?

[2strokebloke]

Take your spark plugs out, and see which ones are fouled to find out which cylinders are not firing properly.

[Jporter12]

Disconnect the vacuum hose going to the fuel pressure regulator. If you see fuel running out of it with the engine running, replace it. That fuel runs right into the intake manifold and would cause your problem, but I'm not so sure it would only be on half the cylinders. Next possibilty is a short to ground in the injector control circuit. The injectors have battery voltage applied to one terminal anytime the ignition it ON. Whenever the other terminal get a ground, that will open the injector, causing fuel to spray. The computer controls the ground circuit. You could have a wire that is pinched or rubbed through allowing it to provide a ground, or the computer could have a problem causing it to apply ground when it shouldn't be. If ya need more info on how to test the circuit, let me know, it's not all that difficult.

[MustangRoadRacer]

yes, it sounds like your injectors are staying open all the time, or at least too long. new injectors won't fix this problem if it is with your computer or the wire as mentioned before.
get a mechanic to troubleshoot your computer, it takes like one hour, and all he has to do is hook up a sensor to your computer, and read the "trouble codes". this is usually pretty cheap, and the first step I would take to diagnosing a problem such as this.

[Jporter12]

Sorry to be contrary here, but pulgging in a scan tool to get trouble codes will most likely NOT tell you anything. I don't recall you saying if you had a check engine light or not, but if you do, it may very well be a RESULT of the excess fuel, or whatever is causing it to dump fuel. I've had many customers some to me and say that "the large parts chain store down the road hooked it up and told me this was bad. I fixed that, now something else is wrong....." when in reality, the same thing is the problem, just they sold them the part for whatever code came up. They're there to sell parts, not fix cars, period. I wish they'd stick to that!

I guess my point here is that the codes are just a pointer to what the problem is. To know for sure what the problem is, things need to be tested. A real scan tools is so much more valuable than a code reader for this reason. It has data available for you to use to diagnose the problem in a convenient box.

[Jporter12]

I will add though, that there are a few codes that have become know as "reliable" because of what the computer has to go through to verify the problem. EGR flow codes on a GM are relatively reliable (needs the EGR passages cleaned), and with OBD2, the catalyst efficiency codes are pretty reliable due to the monitors or "Tests" the computer runs on the O2 sensors that test the converters. I know there are others, but these are 2 that pop into my mind.

[MustangRoadRacer]

if you have an understanding of what the codes actually mean, and know what you'r looking for, they can HELP diagnose an otherwise misleading problem.
they are not the one true answer by any means.